Identification of Destabilized Metal Hydrides for Hydrogen Storage Using First Principles Calculations

Abstract

Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through alloying with other elements. A very large number of possible destabilized metal hydride reaction schemes exist. The thermodynamic data required to assess the enthalpies of these reactions, however, are not available in many cases. We have used first principles density functional theory calculations to predict the reaction enthalpies for more than 100 destabilization reactions that have not previously been reported. Many of these reactions are predicted not be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low. More importantly, our calculations identify five promising reaction schemes that merit experimental study: 3LiNH(2) + 2LiH + Si --> Li(5)N(3)Si + 4H(2), 4LiBH(4) + MgH(2) --> 4LiH + MgB(4) + 7H(2), 7LiBH(4) + MgH(2) --> 7LiH + MgB(7) + 11.5H(2), CaH(2) + 6LiBH(4) --> CaB(6) + 6LiH + 10H(2), and LiNH(2) + MgH(2) --> LiMgN + 2H(2).

High capacity hydrogenstorage materials: attributes for automotive applications and techniques for materials discovery

“…37,99,113,[122][123][124][125][126] This approach can vastly improve the useful throughput of experiments by narrowing the phase space of candidate materials to those exhibiting thermodynamic potential.…”

“…Although the destabilization concept dates to the 1960s, 36 37,99,122,123 and examined by experiment. 35,38,40 Another potential avenue for altering thermodynamics is via extreme reduction in particle size.…”

LiSc(BH4)4: A Novel Salt of Li+ and Discrete Sc(BH4)4− Complex Anions

“…[2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The dehydrogenation of lithium and Group II borohydrides is plagued by severe kinetic limitations and irreversibility that precludes the utilization of these compounds under practical conditions, [2][3][4][5][6][7][8][9][10] even as components of binary hydride mixtures. [12][13][14][15][16][17][18] Many transition metal borohydride complexes also have suitable gravimetric hydrogen densities. 19 However, neutral transition metal borohydride complexes, such as Zr(BH 4 ) 4 , can be eliminated a priori from consideration as practical hydrogen carriers because of their high volatility under the conditions required for dehydrogenation.…”

Functional Materials for Sustainable Energy Technologies: Four Case Studies

“…[78] Given the importance of T dec and its "matching" to the various operating temperatures of fuel cells, the notion (2) above arises from "destabilizing" high-weight-percent hydrogen storage materials in an attempt to reduce decomposition temperatures. [83][84][85] Many hydrides of the light chemical elements have DH values larger than the desired range of ca. 20-40 kJ mol À1 H 2 .…”

“…[83][84][85] 3) The cryo-adsorption of hydrogen on high-surface-area materials (e.g., activated carbons, zeolites, or metal-organic frameworks). [86,87] 4) A hybrid solution combining low-DH interstitial hydride approaches with a (moderately) high pressure compressed hydrogen design (e.g., operating at 350 bar with a TiCrMn or related alloy).…”